In the art of tissue making and papermaking in general, many additives have been proposed for specific purposes, such as increasing wet strength, improving softness, or control of wetting properties. For instance, in the past, wet strength agents have been added to paper products in order to increase the strength or otherwise control the properties of the product when contacted with water and/or when used in a wet environment. For example, wet strength agents are added to paper towels so that the paper towel can be used to wipe and scrub surfaces after being wetted without the towel disintegrating. Wet strength agents are also added to facial tissues to prevent the tissues from tearing when contacting fluids. In some applications, wet strength agents are also added to bath tissues to provide strength to the tissues during use. When added to bath tissues, however, the wet strength agents should not prevent the bath tissue from disintegrating when dropped in a commode and flushed into a sewer line. Wet strength agents added to bath tissues are sometimes referred to as temporary wet strength agents since they only maintain wet strength in the tissue for a specific length of time.
Although great advancements have been made in providing wet strength properties to paper products, various needs still exist to increase wet strength properties in certain applications, or to otherwise better control the wet strength properties of paper products.
A need also exists for a composition that provides wet strength properties to a fibrous material, such as a paper web, while also providing sites to bond other additives to the material. For example, a need exists for a wet strength agent that can also be used to facilitate dyeing cellulosic materials, applying a softener to cellulosic materials, and applying other similar additives to cellulosic materials.
The present invention is generally directed to the use of polyvinylamines in fibrous and textile products, such as paper products, in order to control and improve various properties of the product. For instance, a polyvinylamine can be combined with a complexing agent to increase the wet strength of a paper product. The combination of a polyvinylamine and a complexing agent can also be used to render a web more hydrophobic, to facilitate the application of dyes to a cellulosic material, or to otherwise apply other additives to a cellulosic material.
In one embodiment, the present invention is directed to a paper product having improved wet strength properties. The paper product includes a fibrous web containing cellulosic fibers. The fibrous web further includes a combination of a polyvinylamine polymer and a polymeric anionic reactive compound. The polyvinylamine polymer and the polymeric anionic reactive compound can form a polyelectrolyte complex within the fibrous web. The paper product can be a paper towel, a facial tissue, a bath tissue, a wiper, or any other suitable product.
The polyvinylamine polymer can be incorporated into the web by being added to an aqueous suspension of fibers that is used to form the web. Alternatively, the polyvinylamine polymer can be applied to after the web has been formed. When applied to the surface, the polyvinylamine polymer can be printed or sprayed onto to the surface in a pattern in one application. The polyvinylamine polymer can be added prior to the polymeric anionic reactive compound, can be added after the polymeric anionic reactive compound, or can be applied simultaneously with the polymeric anionic reactive compound. The polyvinylamine polymer can be combined with the fibrous web as a homopolymer or a copolymer. In one embodiment, the polyvinylamine polymer is combined with the fibrous web as a partially hydrolyzed polyvinylformamide. For instance, the polyvinylformamide can be hydrolyzed from about 50% to about 90%, and particularly, from about 75% to about 95%.
In general, any suitable, polymeric anionic reactive compound can be used in the present invention. For instance, the polymeric anionic reactive compound can be an anionic polymer containing carboxylic acid groups, anhydride groups, or salts thereof. The polymeric anionic reactive compound can be, for instance, a copolymer of a maleic anhydride or a maleic acid or, alternatively, poly-1,2-diacid.
The polyvinylamine polymer and polymeric anionic reactive compound can each be added to the fibrous web in an amount of at least about 0.1% by weight, particularly at least 0.2% by weight, based upon the dry weight of the web. For instance, each polymer can be added to the fibrous web in an amount from about 0.1% to about 10% by weight, and particularly from about 0.1% to about 6% by weight. It should be understood, however, that greater quantities of the components can be added to the fibrous web depending upon the particular application. For instance, in some applications it may be desirable to add one of the polymers in a quantity of greater than 50% by weight.
As stated above, the polyvinylamine polymer in combination with the polymeric anionic reactive compound increases the wet strength of the web. In one embodiment, the polymers are added to the fibrous web in an amount such that the web has a 25 microliter Pipette Intake Time of greater than 30 seconds, and particularly greater than 60 seconds. The fibrous web can have a Water Drop Intake Time of greater than 30 seconds, and particularly greater than 60 seconds.
In addition to polymeric anionic reactive compounds, in an alternative embodiment, the present invention is directed to products and processes using the combination of a polyvinylamine polymer and a polymeric aldehyde functional compound, a glyoxylated polyacrylamide, or an anionic surfactant. Examples of polymeric aldehyde functional compounds include aldehyde celluloses and aldehyde functional polysaccharides. In this embodiment, a polymeric aldehyde functional compound, a glyoxylated polyacrylamide, or anionic surfactant can be used similar to a polymeric anionic reactive compound as discussed above.
In one embodiment, the present invention is directed to a method for improving the wet strength properties of a paper product. The method includes the steps of providing a fibrous web containing pulp fibers. The fibrous web is combined with a polyvinylamine and a complexing agent. The complexing agent can be a polymeric anionic reactive compound, a polymeric aldehyde functional compound, a glyoxylated polyacrylamide, an anionic surfactant, or mixtures thereof.
In one embodiment, the fibrous web is formed from an aqueous suspension of fibers. The polyvinylamine and the complexing agent are added to the aqueous suspension in order to be incorporated into the fibrous web. In another embodiment, the complexing agent is added to the aqueous suspension while the polyvinylamine is added after the web is formed. In still another embodiment, the polyvinylamine is added to the aqueous suspension, while the complexing agent is added after the web is formed. In still another embodiment, the polyvinylamine polymer and the complexing agent are both added after the web is formed.
In addition to increasing the wet strength of paper products, the process of the present invention can also be used to facilitate dyeing of a fibrous material. For instance, the present invention is further directed to a process for dyeing fibrous materials such as a textile with an acid dye. The process includes the steps of contacting a cellulosic fibrous material with a polyvinylamine and a complexing agent, such as a polymeric anionic reactive compound. Thereafter, the cellulosic fibrous material is contacted with an acid dye. It is believed that the complexing agent holds the polyvinylamine to the cellulosic material while the acid dye binds to the polyvinylamine.
The fibrous material can be a fiber, a yarn, or a fabric. The cellulosic material can be paper fibers, cotton fibers, or rayon fibers.
In addition to applying an acid dye to a fibrous material, a polyvinylamine can be used in accordance with the present invention to bind other additives to the material. For instance, in another embodiment, the process of the present invention is directed to applying polysiloxanes to fibrous materials that have been previously treated with a polyvinylamine in accordance with the present invention.